In a typical electrostatographic printing apparatus, a light image of an original to be copied is recorded in the form of an electrostatic latent image upon a photosensitive member and the latent image is subsequently rendered visible by the application of toner. The visible toner image is then in a loose powdered form and can be easily disturbed or destroyed. The toner image is usually fixed or fused upon a support which may be a photosensitive member itself or other support sheet such as plain paper.
The use of thermal energy for fixing toner images onto a support member is well known. In order to fuse toner material onto a support surface permanently by heat, it is necessary to elevate the temperature of the toner material to a point at which the constituents of the toner material coalesce and become tacky. This heating causes the toner to flow to some extent into the fibers or pores of the support member. Thereafter, as the toner material cools, solidification of the toner material causes the toner material to be firmly bonded to the support.
Typically, thermoplastic resin particles are fused to the substrate by heating to a temperature of between about 90.degree. C. to about 160.degree. C. or higher depending upon the softening range of the particular resin used in the toner. It is not desirable, however, to raise the temperature of the substrate substantially higher than about 200.degree. C. because of the tendency of the substrate to discolor at such elevated temperatures particularly when the substrate is paper.
Several approaches to thermal fusing of toner images have been described in the prior art. These methods include providing the application of heat and pressure substantially concurrently by various means: a roll pair maintained in pressure contact; a belt member in pressure contact with a roll; and the like. Heat may be applied by heating one or both of the rolls, plate members or belt members. The fusing of the toner particles takes place when the proper combination of heat, pressure and contact time are provided. The balancing of these parameters to bring about the fusing of the toner particles is well known in the art, and they can be adjusted to suit particular machines or process conditions.
After repeated fusing cycles, the fusing surface of the fusing member will eventually exhibit unsatisfactory toner release, leading to poor quality prints. Typically, the fuser member is then either tossed away or recycled by stripping off all the coatings and then recoating the substrate to produce a new fuser member. Thus, there is a need, which the present invention addresses, for a more economical method to renew a spent fuser member.
Fuser members and their fabrication methods are disclosed in Del Rosario, U.S. Pat. Nos. 5,035,950; Chow, 4,876,777; and Evans et al., 4,465,646.
The present inventors believe the fuser members described in Clifford O. Eddy et al. U.S. appln. Ser. No. 08/572,212 and Chen et al., U.S. Pat. No. 5,595,823 (assigned to Eastman Kodak Company), the disclosures of which are hereby totally incorporated by reference, may be renewed in embodiments of the present invention.